In many application it is desirable to know at a remote location the exact position of a collar on a shaft. Such applications include the automotive and aircraft industries or any other area where mechanical relationships of parts are of interest.
Several types of sensors have been developed for such applications. The simplest sensor would be a mechanical linkage from the part sought to be monitored to a dial. Such sensors become generally impractical where the area where the information is needed is a distance from the part being monitored.
To overcome the limitations of mechanical sensors many types of electrical sensors have been developed. Such sensors include potentiometer, magnetic pickups of various types, optical pickups, and capacitive pickups. In the common application of a servo system the pickups are generally potentiometer or resolvers.
In these general applications the property being measured is angular position. In those cases where longitudinal position is sought to be sensed a mechanical linkage is often provided to convert the longitudinal position into an angular position. In some cases a sensor specially adapted to sense longitudinal position is provided.
In those applications where it is desired to determine both the angular and axial position of one part relative to another a combination of two sensors is generally used. As an alternative a single sensor has been proposed which may be altered in position to sense both factors.
In applications such as inside a drive train or engine the sensor must be capable of working this environment for extended periods of time at elevated temperatures and pressures. It is also desirable if the sensor can function as a bearing between the two parts. Accordingly there is a need for a sensor that can provide information about both the angular and axial relative position of two parts while it functions as a bearing.